Journal of Volcanology and Geothermal Research最新文献

{"title":"Conduit armouring preceding explosive activity at an andesitic stratovolcano, an example from Taranaki Mounga, New Zealand","authors":"","doi":"10.1016/j.jvolgeores.2024.108214","DOIUrl":"10.1016/j.jvolgeores.2024.108214","url":null,"abstract":"<div><div>The strength and permeability of volcanic conduits can directly influence eruption dynamics via moderating the outgassing of ascending magma and the density of eruption plumes. Lithic clasts in pyroclastic ejecta can be used to understand the dynamic evolution of conduit walls because they are incorporated into the ascending melt-gas-particle mixture during volcanic eruptions. We examine the 1655 CE Burrell eruption of Taranaki Mounga, which transitioned from effusive activity to an explosive sub-Plinian phase and ended in unsteady columns. This episode was followed by a series of effusive eruptions of lower explosivity. Using textural analysis and physical properties, we distinguish five dominant lithic clast types within Burrell deposits that represent different regions of the shallow conduit and vent. Lithic types 1–3 represent juvenile (‘intrusive cognate’) and older (‘intrusive accessory’) conduit-filling plug materials. Lithic type 4 represents juvenile (‘extrusive cognate’) vent-filling lava dome extruded at the eruption onset, while Type 5 lithics (‘extrusive cognate’) represent sintered/compacted cognate material from the shallow vent accumulated during transitions in eruptive style. Crystalline andesite lithics (type 1) show a microlite-dominated groundmass. Hydrothermally altered andesite lithics (type 2) show breakdown of phenocrysts and increased seismic velocity relative to type 1 lithics. Brecciated andesite lithics (type 3) comprise fractured and sintered clasts of crystalline andesite. Glassy andesite lithics (type 4) show sub-rounded vesicles and glass-hosted microlites. Banded vitrophyre lithics (type 5) show bands of varying vesicularity, crystallinity and clast load. Physical property data reveals porosity, fracturing, sintering and alteration extent dictate dynamic changes in conduit permeability and potentially strength. Our results show how, during the explosive phase of the Burrell eruption, the conduit was lined with juvenile and remnant shallow plug material that was variably fractured, sintered and altered before being eroded and ejected. Comparison with previous work on Taranaki and dome-plug material from around the world shows how fracturing and sintering of conduit walls, combined with lining with dense juvenile material, cause overall permeability reduction and strengthening of the conduit. This inhibits outgassing and preserves conduit structure, facilitating the transition to explosive activity and the establishment of a stable eruption column.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142561203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Volcanic tremor associated with successive gas emission activity at a boiling pool: Analyses of seismic array and visible image data recorded at Iwo-Yama in Kirishima Volcanic complex, Japan","authors":"","doi":"10.1016/j.jvolgeores.2024.108212","DOIUrl":"10.1016/j.jvolgeores.2024.108212","url":null,"abstract":"<div><div>Volcanic tremors are often observed during volcanic activity and volcanic eruptions, and their generation processes provide clues for understanding volcanic fluid activity underground and eruption dynamics. However, tremors are characterized by continuous oscillations that mask P- and S-waves; hence few studies have precisely located the source, which is the most fundamental information for understanding the generation mechanism. In this study, we focus on volcanic tremors excited by continuous gas emissions occurring at a vent called Y2a in Iwo-Yama, the Kirishima Volcanic Complex, Japan, to clarify the source process of the tremor as well as gas emission activity. We simultaneously observed the volcanic tremor by deploying a small aperture array consisting of six seismometers and the gas emission activity by using a newly developed visual IoT system that can be operated without commercial electricity. MUSIC analysis locates the tremor at depths ranging from the ground surface to approximately 200 m beneath the Y2a and Y2b vents, which are approximately 30 m apart, for approximately four months from November 2021 to February 2022. The source locations of the tremors in the 2 Hz (1.2–2.6 Hz), 4 Hz (3–4 Hz), and 5 Hz (4–5.5 Hz) ranges show some differences and changes with time. The source location tends to become deeper when the 2 Hz amplitude is large. The infrasound generated by gas emission activity is dominant in the tremor signals, which are recognized in the wave propagation velocity with an acoustic velocity of 330 m/s when the 2 Hz amplitude is small. The visual IoT system succeeded in detecting long-term changes in the gas emission activity, and we found that the 2 Hz amplitude of tremor was well correlated with the amount of hot water in the boiling pool of Y2a, which was controlled by precipitation and evaporation during non-rainy days. From these observations, we infer that the volcanic tremor is generated by resonance of volcanic gas and hot water in a crack-like structure beneath Y2a. The resonance was triggered by the counterforces of the gas emissions in the boiling pool, and the infrasound was dominant during periods of hot water depletion in the boiling pool. Temporal changes in the source depths may be caused by changes in the fluid properties, configuration of the resonator and/or the strengths of the underground sources and infrasound. Our simultaneous observations of seismic array and visual IoT system clarify that even the continuous gas emission activity that looks stable is controlled by external sources such as precipitation.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spread and frequency of explosive silicic volcanism of the Carpathian-Pannonian Region during Early Miocene: Clues from the SW Pannonian Basin and the Dinarides","authors":"","doi":"10.1016/j.jvolgeores.2024.108215","DOIUrl":"10.1016/j.jvolgeores.2024.108215","url":null,"abstract":"<div><div>Explosive silicic volcanism of the Carpathian-Pannonian Region (CPR) is increasingly recognized as the primary source of tephra across the Alpine-Mediterranean region during the Early and Middle Miocene. However, the tephrostratigraphic framework for this period of volcanic activity is still incomplete. We present new multi-proxy data from Lower Miocene ignimbrites and tephra fallout deposits from the southwestern CPR and the Dinaride Lake System and integrate them into existing datasets to better resolve the regional extent and scale of these eruptions of the CPR. Volcanic glass geochemistry indicates distal fallout tuffs deposited in the Sinj Basin are correlative with the proximal Ostoros ignimbrites from the Bükkalja Volcanic Field, indicative of regionally extensive volcanism at 17.295 ± 0.028 Ma, based on CA-ID-TIMS U<img>Pb zircon geochronology. Based on integrated tephrostratigraphic data, newly identified 17.064 ± 0.010 Ma massive rhyolitic ignimbrite deposits from the Kalnik Volcaniclastic Complex located in the southwestern CPR are correlative with the 17.062 ± 0.010 Ma Mangó massive ignimbrite found in the Bükkalja Volcanic Field located in the northern CPR. Based on these new observations of its potential areal distribution and estimated thicknesses, these two widespread ∼17.1 Ma ignimbrites represent intermediate to large caldera-forming ignimbrites, larger than previously suggested. Finally, volcanic glass geochemistry of fallout deposits from the Dinaridic Sinj and Livno-Tomislavgrad Basins have similar volcanic glass geochemistry as the rhyolitic pumices from the lowermost part of the Bogács ignimbrite unit of the Bükkalja Volcanic Field. However, high-precision geochronology indicates that these distal ashfalls were deposited at 16.9567 ± 0.0074 Ma, significantly predating the 16.824 ± 0.028 Ma emplacement of the fiamme-bearing part of the Bogács ignimbrite. These distinct ages suggest that the Bogács unit represents multiple eruptive events and indicating that further work is required to deconvolve this portion of the CPR volcanic record. Together, these data suggest that large volume CPR ignimbrite volcanism was more frequent and widespread than previously understood, enhancing the existing volcanic framework and history of the source region for this time period.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142572255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Melt viscosity tracks the volcanic and magmatic evolution of the 2021 Tajogaite eruption, La Palma (Canary Islands)","authors":"","doi":"10.1016/j.jvolgeores.2024.108210","DOIUrl":"10.1016/j.jvolgeores.2024.108210","url":null,"abstract":"<div><div>After more than 50 years of repose, on September 19th, 2021, a volcanic eruption began at the Cumbre Vieja ridge on La Palma, Canary Islands. The combined effusive and explosive activity generated a &gt; 12 km² lava flow field with a new cone nearly 200 m higher than pre-eruptive topography and a vast tephra blanket. The immediate impact was locally devastating, destroying nearly 2000 buildings, blocking two main and numerous secondary roads, and inundating high-value agricultural land.</div><div>The hybrid nature of the eruption and the observed variations in eruption intensity motivated a thorough investigation of bulk liquid viscosity at high temporal resolution. Collection of 82 lava samples was achieved at a near daily resolution over the course of the 85-day-long event (through the end of the eruption on December 13th, 2021). All the samples were remelted, and liquid viscosity was measured in a concentric cylinder viscometer from 1490 °C down to incipient crystallization temperatures. These data constitute the highest temporal resolution viscosity dataset obtained for an eruptive sequence to date.</div><div>A tripartite viscosity pattern is identified at isothermal conditions: 1) during the fissure opening and establishing stage (days 1–20) a linear decrease in melt viscosity occurred; 2) during most of the eruption duration (days 21–70) viscosity was constant and 3) from day 70 until the end of the eruption viscosity increased again. We interpret this pattern as magma being extracted from different parts of the plumbing system over the course of the eruption. Accordingly, we show that viscosity time series can help shed light on some of the complexities of volcanic plumbing system. Additionally, the presented results highlight the monitoring potential of the viscosity assessment approach, specifically in regard to forecasting eruption behavior using direct information about magma mobility and detecting changes in magmatic plumbing system dynamics.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The pre-Campi Flegrei caldera (>40 ka) explosive volcanic record in the Neapolitan Volcanic Area: New insights from a scientific drilling north of Naples, southern Italy","authors":"","doi":"10.1016/j.jvolgeores.2024.108209","DOIUrl":"10.1016/j.jvolgeores.2024.108209","url":null,"abstract":"<div><div>The oldest volcanism documented in near-vent sections around the Campi Flegrei (CF, southern Italy) caldera does not exceed ∼78 ka, even though the mid- to ultra-distal tephrostratigraphic record would suggest that activity in this area started well before that. Reconstructing the activity preceding the large caldera-forming Campanian Ignimbrite (CI) eruption of ∼40 ka, via surface geological surveys in proximal areas, is challenging because of the poor accessibility and paucity of sections recording the older chronostratigraphic interval. In order to fill the gap in knowledge of the activity preceding the CI eruption, a 113.2 m deep scientific drillhole was emplaced in the Ponti Rossi area, in the northern part of the city of Naples. The Ponti Rossi area was selected as representative of the stratigraphic setting prior to the CF caldera formation because it is close, although external, to any proposed caldera rim or downthrown area. The cored succession, consisting of pyroclastic deposits separated by paleosols, reworked humified deposits or subaerial erosional surfaces, has been logged and sampled for sedimentological, mineralogical, and geochronological analyses. Thirty-one Pyroclastic Units (PU) were identified. Based on the structural/textural features of the recovered sediments, the first relevant result is the possible absence of the CI, while the deposits of the ∼15 ka Neapolitan Yellow Tuff eruption, the second largest caldera-forming event of CF, represent the shallowest sediments. ⁴⁰Ar/³⁹Ar age determinations on alkali feldspars, extracted from juvenile fragments collected at 45.8–45.9 (PU-29) and 99.5–99.6 (PU-1) metres of depth, yielded ages of 59.03±0.50 ka and 110.00±0.35 ka, respectively. The age obtained for the deepest cored unit, having sedimentological characteristics compatible with proximal deposition, represents the oldest age obtained for a pyroclastic deposit in the sequences near the CF caldera boundaries and extends by 30 ky the explosive history of this area. Furthermore, based on ⁴⁰Ar/³⁹Ar age constraints, at least 29 eruptions, spanning the ∼59–110 ka interval, can be added to the volcanic history of the Neapolitan Volcanic Area. These eruptions can be largely attributed to the CF area, prior to the CI caldera formation, and testify to hitherto unknown, intense explosive activity.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534471","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unique seismic and eruption precursors to the 1996 and ongoing magmatic eruptions of Popocatépetl: Coupled and fluidized bed events","authors":"","doi":"10.1016/j.jvolgeores.2024.108208","DOIUrl":"10.1016/j.jvolgeores.2024.108208","url":null,"abstract":"<div><div>We describe three unique types of seismicity at Popocatépetl volcano that accompanied the initial vent-clearing eruptive activity in December 1994 through the eruption of the first two domes in 1996. We identify and describe two types of coupled events, 1) spasmodic burst coupled events, a burst of volcano tectonic (VT) events coupled with a large eruptive explosion (21 December 1994 and 5 March 1996), and 2) explosion-couplet coupled events, a pair of events with a deeper first event and whose second event correlates with a small gas emission or explosion. Explosion-couplets occurred with the onset of magmatic ash dominated eruptions and their properties are very useful for forecasting magmatic eruptions at Popocatépetl volcano. Measurable quantities including the time between the first and second phase, daily numbers of events, and the amplitude ratio between the second and first phase systematically changed as the first two domes approached the surface between March and June 1996. Interevent times decreased from many tens of seconds to a few seconds, while amplitude ratios increased from about 2 to 10 or more. Event numbers increased prior to and during initial dome extrusion. These changes were used to forecast the eruption of the first two domes. We also report on another unusual type of low frequency seismicity that accompanied emissions called fluidized bed events. Fluidized bed events occurred following the initial eruption on 21 December 1994, beginning mid-January 1995, when SO₂ emissions were initially elevated, and the conduit was open. Fluidized bed events began to wane in late March through the end of May 1995 as did SO₂ emissions. Consistent gas, visual and seismic observations by Centro Nacional de Prevención de Desastres (CENAPRED) enabled the direct correlation of the gas, magma, and seismic phenomena.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Improved volcanic SO2 flux records from integrated scanning-DOAS and UV Camera observations.","authors":"","doi":"10.1016/j.jvolgeores.2024.108207","DOIUrl":"10.1016/j.jvolgeores.2024.108207","url":null,"abstract":"<div><div>Volcanic SO₂ flux is a key indicator of magma influx into shallower portions of magmatic plumbing systems, and as such is central to volcano monitoring. However, observations have traditionally been challenged by a variety of technical and methodological caveats and limitations, to overcome which it is required an intercomparison of different observational techniques and, where possible, their integration. Here, we compare ∼9 years (2014 to 2022) of SO₂ flux records at Stromboli obtained through (i) a near-vent (∼500 m) UV Camera system and (ii) a network of DOAS spectrometers scanning the distal (∼2 km) bulk plume. We find a large (133 t/d on average) systematic offset between the SO₂ flux time-series streamed by the two observational techniques, with the flux from the scanning spectrometers being ∼200 % higher on average than UV Camera flux. We propose this mismatch to derive from a combination of (i) SO₂ flux underestimation by the UV Camera, as caused by incomplete coverage of the plume (due to topography of the crater area) and radiative transfer issues in the optically dense, near-vent plume, and (ii) SO₂ flux overestimation by the distal scanning spectrometers', caused by non-ideal (incomplete) atmospheric dilution of source-released gas puffs during atmospheric transport. Our analysis suggests this latter process to be dominant, imparting a positive wind speed dependence and a marked seasonality to the distal scanning spectrometers' fluxes, and causing them to significantly overestimate the source SO₂ fluxes. Finally, we propose a novel integrated SO₂ flux record, based on the combination of UV Camera-derived gas velocities and DOAS-derived SO₂ integrated column amounts (back-calculated at source using an experimentally derived plume dilution function). We expect this SO₂ flux time-series to be less affected by external factors (e.g., meteorological, illumination and volcano topography conditions) than using any of the two techniques alone and hence a better proxy of volcano behaviour. We recommend testing of the integrated UV Camera-scanning-DOAS method at other volcanoes to explore its utility for improved volcanic degassing characterization.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142534470","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Melt generation and magma storage conditions of primitive arc lavas in the Macolod Corridor, southwestern Luzon arc, Philippines","authors":"","doi":"10.1016/j.jvolgeores.2024.108206","DOIUrl":"10.1016/j.jvolgeores.2024.108206","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Decoding the origin of primitive arc magmas from petrological, geochemical, and thermobarometric constraints is crucial for understanding their melt generation process and crustal storage conditions. In the Philippine arc setting, primitive basalts have been recognized in the Macolod Corridor, southwestern Luzon arc. The Macolod Corridor is a 30 by 60-km northeast-southwest striking, young rift system that hosts several Quaternary stratovolcanoes including the active Taal Volcano and Mt. Banahaw, lava domes, and ∼ 200 monogenetic centers classified as scoria cones, tuff cones, tuff rings, and maars. This study reports textural, petrological, and geochemical analyses of the Macolod primitive basalts to decipher their petrogenesis and elucidate their pre-eruptive magma storage conditions. We identified at least five distinct primitive lava compositions based on their modal mineralogy: clinopyroxene-olivine basalts, plagioclase-olivine-clinopyroxene basalts, olivine-plagioclase-clinopyroxene basalts, clinopyroxene-plagioclase-olivine basalts, and clinopyroxene-olivine-plagioclase basalts. Clinopyroxene-olivine basalts and clinopyroxene-plagioclase-olivine basalts occur as lapilli and bomb deposits. In contrast, plagioclase-olivine-clinopyroxene-basalts, olivine-plagioclase-clinopyroxene basalts, and clinopyroxene-olivine-plagioclase basalts occur as lapilli and volcanic bombs in monogenetic volcanoes and as basaltic blocky lava flows in small polygenetic volcanoes. Phenocrysts, glomerocrysts, and microphenocrysts assemblages include olivine, clinopyroxene, plagioclase ± spinel in a glassy matrix. The basalts are identified as subalkaline, medium-K, and medium-Fe tholeiitic basalts, based on their bulk-rock geochemistry. Adding 3&lt;strong&gt;–&lt;/strong&gt;4 % equilibrium olivine to the Macolod primitive basalts generates magmas in equilibrium with mantle olivines with Fo&lt;sub&gt;90.68&lt;/sub&gt;&lt;sub&gt;–&lt;/sub&gt;&lt;sub&gt;90.82&lt;/sub&gt; and 0.392&lt;strong&gt;–&lt;/strong&gt;0.395 wt% NiO compositions. Disequilibrium textures exhibited by olivines, clinopyroxenes, and plagioclases suggest that these are products of magma decompression and dissolution processes. Calculated melt based on olivines reveals that these primitive magmas last equilibrated at depths ranging from ∼36&lt;strong&gt;–&lt;/strong&gt;42 km (1.03&lt;strong&gt;–&lt;/strong&gt;1.23 GPa) at 1286°&lt;strong&gt;–&lt;/strong&gt;1318 °C. Application of clinopyroxene-only thermobarometer results indicate clinopyroxene crystallization depths of around 7&lt;strong&gt;–&lt;/strong&gt;16 and 10&lt;strong&gt;–&lt;/strong&gt;19 km for hydrous and anhydrous estimates, respectively. The segregation depths estimated in this study translate to the uppermost mantle until near the Moho boundary whereas the storage depths correspond to prolonged magma storage regions in the upper crust as modeled by existing geophysical data (i.e., seismic travel-time tomography). Combining textural and geochemical results from this study with existing geophysical data provides new insights into the magma plumbi","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Conditions for formation and preservation of andesite-hosted mafic enclaves during the 2018 Lower East Rift Zone eruption of Kīlauea","authors":"","doi":"10.1016/j.jvolgeores.2024.108205","DOIUrl":"10.1016/j.jvolgeores.2024.108205","url":null,"abstract":"<div><div>Andesites erupted at Kīlauea in 2018 in the Lower East Rift Zone for the first time in the known geological record. The evolved lavas erupted at Fissure 17 of the 2018 eruption, ranging from andesites to basaltic andesites, contain abundant mafic enclaves both in the lava flows and the ejecta, which are unusual at Kīlauea and in Hawai'i in general. Textural observations indicate that the enclaves originate from incomplete mixing of two magmas rather than the incorporation of cold basaltic wall rock. We suggest, on the basis of bulk and mineral compositions, that the source of the mafic enclaves is the early 2018 evolved basalt magma (phase 1b) that erupted concomitantly at adjacent fissures, which mixed with the andesite to produce the range of basaltic andesite compositions observed at Fissure 17. The coexistence of homogenized basaltic andesites and mafic enclaves within the same magma require a mixing mechanism resulting in both complete homogenization and preservation of enclaves. We propose that the range of mixing and mingling processes may be explained by spatial and temporal variability in the mixing percentages of the phase 1b basalt and the andesite within the andesite magma chamber. Field observations, chemical compositions, and 2D thermal conduction models suggest that enclaves are preserved where the basalt contribution to mixing is less than roughly 40 %, as a result of microlite crystallization leading to rigidification of the enclave magma. Above this threshold, the mixed magmas became largely homogenized. The scarcity of mafic enclaves at Kīlauea and in the Hawai'i igneous record is likely explained by mixing between magmas that lack sufficient compositional and rheological contrasts to preserve them.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Satellite measurement of forest disturbance, recovery and deposit distribution following explosive volcanic eruptions","authors":"","doi":"10.1016/j.jvolgeores.2024.108204","DOIUrl":"10.1016/j.jvolgeores.2024.108204","url":null,"abstract":"<div><div>The characteristics and extent of forest damage, and the subsequent patterns of recovery, reflect the intensity of an explosive volcanic eruption and have the potential to be a novel proxy for eruption magnitude and impact. Using satellite measurements of vegetation damage and recovery patterns, following the 2015 explosive eruption of Calbuco, Chile, we assess the impact on surrounding temperate forests and how areas impacted by different deposit types recover post-eruption. The Calbuco eruption resulted in tephra deposition over hundreds of square kilometres, pyroclastic flows extending 6 km and lahars extending 15 km. We explore NDVI derived from optical imagery (June 2013–May 2023) as well as radar backscatter and phase coherence (October 2014–June 2023) through time series analysis, clustering and estimation of recovery timescales to find patterns in forest disturbance and recovery. We find that forest damage and recovery correspond primarily with deposit type, thickness and dispersal directions. The thickest tephra deposits (<span><math><mo>&gt;</mo></math></span> 40 cm) correlate with the most vegetation loss, so our vegetation impact maps allow us to refine the spatial mapping of tephra fall-deposit isopachs to give a revised eruption volume of 0.28 km³. Vegetation recovery rates relate to initial impact type and intensity, but also local topography, aspect and altitude. Our results demonstrate a novel application of optical and radar satellite remote sensing to determine eruption extents and magnitudes through vegetation disturbance. We show that measuring vegetation disturbance, particularly in remote and densely vegetated environments, can help refine field-based analyses in inaccessible or intensely damaged zones.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142432207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}